This application claims benefit of Japanese Patent Application No. 2001-359931 filed on Nov. 26, 2001, the contents of which are incorporated by the reference.
The present invention relates to biometrics identification systems for individual identification and, more particularly, to fingerprint identification method and system.
With recent rapid spread of portable telephone systems, it has been estimated to utilize portable telephone systems for purchasing products and making settlement there for in electronic business transactions. An individual identification system of high identification accuracy for making settlement in portable telephone system, thus has been demanded.
As for the prior art individual identification system, there are various technical methods, such as a technique of individual identification by using a physical property such as a key or a card, a technique of individual identification by using person's intelligence such as passwords, biometrics identification for individual identification by using feature data of body and techniques which are combinations of such techniques. However, the technique of individual identification by using a physical property has a drawback in that the physical property may be lost or stolen. In the identification technique using such intelligence as passwords, however, although the operation is easy and ready, the intelligence may be forgotten or stolen. Particularly, for realizing high identification accuracy, the number of key digits has to be increased, thus extremely deteriorating the convenience of handling.
In the biometrics identification technique utilizing feature data (biometrics) peculiar to the body such as fingerprints, voiceprints, faces and irises, on the other hand, the body data is neither lost, stolen nor forgotten.
Among the above identification systems, the fingerprint identification technique is thought to be promising from the standpoints of the size, cost and identification accuracy.
In the fingerprint identification technique, the identification is made by detecting patterns or features of raised parts (or raised lines) of fingerprints. The fingerprint identification system comprises a fingerprint identification module, which includes a fingerprint sensor part for reading out and detecting fingerprints as fingerprint patterns, a fingerprint registering part for preliminarily registering fingerprint patterns as identification templates in a memory, and a fingerprint identifying part for comparing and collating, at the time of identification, a fingerprint pattern (i.e., sample) detected in the fingerprint sensor part with the registered fingerprint pattern or patterns. The fingerprint sensor comprises a group of minute sensor pixel cells arranged at a pitch of, for instance, 50 to 100 μm, and it detects raised and recessed parts of a fingerprint. Various fingerprint pattern detecting systems are available for use in the fingerprint sensor. Among these systems are mainly an electrostatic capacitance system and an optical system. In the electrostatic capacitance system, for instance, as shown in FIG. 5, a Si (silicon) semiconductor element is used as substrate. Raised and recessed parts 14 and 15 of the fingerprint are detected with detection as fingerprint pattern, by individual cells 11, of capacitance 12 defined by the distance and the area of contact between the surface of a finger 13 and the substrate.
As the measure of the identification accuracy which is an important measure in the identifying technique, there are FAR (Fault Acceptance Ratio) and FRR (Fault Rejection Ratio). The FAR represents the probability of erroneously accepting a fault person as registered person (that is, per cent ratio of fault acceptance cases to fault persons, who are tested for identification). The FRR represents the probability of erroneously identifying a registered person as non-registered person and making a rejection (that is, per cent ratio of erroneous rejection cases to registered persons, who are tested for identification). The smaller are these values, the identification system can be said to have the higher identification accuracy.
As the identification accuracy in the present fingerprint identification techniques, FAR=0.0002% or below and FRR=0.05% or below are realized in fingerprint identification systems mounted in PC, work station, etc.
In the prior art fingerprint identification system, the fingerprint of the identified person is collated for identification with respect to only one finger. In this system, the FAR and FRR are provided, and their values in the fingerprint identification module correspond to the identification accuracy of the system.
As prior art, Japanese Patent Laid-Open No. 4-098370 discloses a system for fingerprint identification by using a plurality of fingers. In this system, the plurality of fingers are simultaneously inputted to the sensor for collation and identification. Japanese Patent Laid-Open No.10-154231discloses an identification system for making identification by taking the order of a plurality of times of fingerprint inputting into considerations. In both the above prior art techniques, a plurality of fingers are used for identification. However, by so doing sufficient identification accuracy may not always be obtained. In addition, in both the above techniques it is possible to improve the FAR, but doing so leads to deterioration (or increase) of the FRR.
In the case of making a high price product settlement in an electronic business transaction or the like, the identification system should have a high identification accuracy. As described before in connection with the prior art, in the fingerprint identification technique a high identification accuracy is realized. To realize high identification accuracy, however, high performance processor and high capacity memory are necessary, leading to high system price. At present, limitations are imposed on the processor performance and memory capacity that can be provided in the portable telephone set. Therefore, it is difficult to mount a fingerprint identification module having high identification accuracy as noted above.